Self-Healing, Recyclable, and Degradable Castor Oil-Based Elastomers for Sustainable Soft Robotics

Self-healing polymers render their life cycle more sustainable by recovering their properties upon healing. Intrinsic self-healing polymers can be recycled, which further reduces waste production. Yet, despite these intrinsic benefits, several sustainability issues remain largely neglected, including the use of fossil-derived materials, hazardous chemicals, and the material management at the end of its life. Herein we report a series of castor oil-based self-healing elastomers that account for these challenges and show improved mechanical and self-healing capabilities compared to the other bio-based self-healing materials. Castor oil was functionalized using a simple, one-pot, solventless synthesis from renewable resources and crosslinked by Diels-Alder cycloaddition. They can be reprocessed and recycled, or hydrolytically degraded at the end of their service life. The mechanical properties of the materials can be tuned (Young’s modulus 0.5-20 MPa), with a fracture strain of up to 487%. A fracture strain of 100% could already be recovered after just 60 seconds at room temperature, and 75% of the mechanical properties after just 24 h. By taking advantage of these properties, a soft pneumatic gripper has been developed, capable of healing autonomously which is fully recyclable and degradable. Hence, we provide a sustainable alternative for soft-robotics applications and for self-healing elastomers in general.